I go through this little song and dance every time I start a book. I'm hoping Kobo will fix this and the sleepcover bug in the next release.

Did you try what I posted above? Simply return to the home screen after opening a new book before the device goes to sleep should prevent the wrong cover from being used. But, once the wrong sleep cover is associated with a book, it needs the song and dance to fix it.

I expect that Kobo will have THIS bug fixed in the next release. But, they seem to be able to find lots of different ways to mess up the sleep cover, so there might be a different bug.